This research examines the occurrence of acute and chronic depression in a large, heterogeneous metropolitan area. The major objectives are to assess causal factors and outcomes associated with this condition, including physical health status, life event stressors, social support networks, health care utilization, and help-seeking behavior. Longitudinal panel data will be used in linear structural relationship models to assess the relative effects of reciprocal causation between mental and physical health status. In addition, the mediating effects of social support networks in buffering between stress and psychiatric health status will be examined. With the use of a prospective study design, a random sample of 1,000 adults representative of the Los Angeles county population are initially being interviewed in a household survey and followed up quarterly by telephone interviews. The final interview will be either a face-to-face or telephone interview, depending upon random assignment. A control group of 250 additional persons will be used at the final interview to investigate panel effects. The major instrument for classifying depression will be the NIMH CES-D scale. This project will examine the role of social support systems on the use or nonuse of community mental health and general medical resources by individuals identified as depressed. The relationship between cigarette smoking, alcohol consumption, and use of medications and depressive symptomatology will be examined.